Final answer:
Before a blood transfusion, a nurse should measure the patient's blood type through cross matching to ensure compatibility and prevent reactions. Type O blood is used in extreme emergencies when there's no time to determine blood type. Ensuring proper access and fluid availability for significant blood loss is also critical.
Step-by-step explanation:
Before starting a blood transfusion, it is vital for a nurse or healthcare professional to measure and cross match the patient's blood type with the donor blood. Cross matching is crucial to ensure compatibility and prevent any potentially harmful reactions, such as a hemolytic transfusion reaction (HTR). In certain emergency situations, where there is severe bleeding and no time for blood type determination, type O blood can be used as it is the universal donor type. Additionally, the patient may have a blood type test conducted before a scheduled surgery; antibodies are added to patient blood samples, and the presence of agglutination with anti-A and anti-B antibodies indicates the blood type. In the described case, visible agglutination in both wells suggests the patient has AB blood type. Also, prior to a transfusion, ensuring that there is appropriate access and sufficient fluids available for a patient who is at risk of losing at least 500 ml of blood (or 7 ml/kg in children) is essential.